Cementing operations are used in wellbores to fill the annular space between casing and the formation with cement. Once set, the cement helps isolate production zones at different depths within the wellbore. Currently, cementing operations can flow cement into the annulus from the bottom of the casing (e.g., cementing the long way) or from the top of the casing (e.g., reverse cementing).
Due to weak earth formations or long strings of casing, cementing from the top or bottom of the casing may be undesirable or ineffective. For example, when circulating cement into the annulus from the bottom of the casing, problems may be encountered because a weak earth formation will not support the cement as it rises on the outside of the annulus. As a result, the cement may flow into the formation rather than up the casing annulus. When cementing from the top of the casing, it is often difficult to ensure the entire annulus is cemented.
For these reasons, staged cementing operations can be performed in which different sections (i.e., stages) of the wellbore's annulus are filled with cement. To do such staged operations, various stage tools can be disposed on the tubing string in the casing for circulating cement slurry pumped down the tubing string into the wellbore annulus at particular locations.
As an example, FIG. 1A illustrates an assembly according to the prior art having a stage tool 24 and a packer 22 on a casing string or liner 20 disposed in a wellbore 10. The stage tool 24 allows the casing string 20 to be cemented in the wellbore 10 using the two or more stages. In this way, the stage tool 24 and staged cementation operations can be used for zones in the wellbore 10 experiencing lost circulation, water pressure, low formation pressure, and high-pressure gas.
As shown, an annulus casing packer 22 can be run in conjunction with the stage tool 24 to assist cementing of the casing string 20 in two or more stages. The stage tool 24 is typically run above the packer 22, allowing the lower zones of the wellbore 10 to remain uncemented and to prevent cement from falling downhole. One type of suitable packer 22 is Weatherford's BULLDOG ACP™ annulus casing packer. (ACP is registered trademarks of Weatherford/Lamb, Inc.)
Other than in a vertical bore as shown in FIG. 1A, stage tools can be used in other implementations. For example, FIG. 1B illustrates a casing string 20 having a stage tool 24 and a packer 20 disposed in a deviated wellbore. As also shown, the assembly can have a slotted screen 26 below the packer 22.
Two main types of stage tools are used for cementing operations. Hydraulic stage tools are operated hydraulically using plugs. Although hydraulic operation can decrease the time required to function the stage tools, the seats and plugs in these stage tools need to be drilled out. The other type of stage tool is a mechanical port collar, which does not require drill-out. However, these mechanical collars require a more complex operation that uses a workstring to function the collars.
FIG. 2 illustrates a mechanical cement port tool 30 according to the prior art in partial cross-section. The tool 30 is run on casing string (not shown) and includes a housing 32 with a through-bore 34. Exit ports 36 communicate cement slurry from the through-bore 34 into a wellbore annulus during cementing operations. To open and close flow, a mechanically shifted sleeve 40 is disposed in the through-bore 34 and can be moved relative to the exit ports 36 to close and open communication therethrough. In the closed position shown, seals 46 on the sleeve 40 seal off the exit ports 36, and a lock ring 45 rests in a lower profile 35 of the housing's through-bore 34.
The sleeve 40 has upper and lower profiles 48a-b used to shift the sleeve mechanically with a shifting tool 50, such as shown in FIG. 3. The shifting tool 50 has a body 54 that couples to a worksting 52. Engagement profiles 58, such as B-profiles, on the outside of the body 58 can engage in the sleeve's profiles 48a-b so that mechanical manipulation of the workstring 52 can manipulate the sleeve 40.
Currently, when doing a two stage cementing application, the inner string 52 is used to manipulate the mechanical port collar's sleeve 40 to allow the ports 36 to be exposed to the annulus so cement slurry can be pumped out of the collar 30. This requires extra rig time to run the workstring 52 in the hole, function the collar 30, and come out of the hole with the workstring 52.
For example, FIG. 4A shows an example of the port collar 30 as it is run in the hole. The mechanical port collar 30 is made up and run in the well on either the casing or liner. Shown in the closed position, the sleeve 40 closes off the collar's ports 36. The collar 30 is a full-bore cementing valve that is opened and closed with axial workstring movement and requires no drill-out after use. Therefore, plugs or seats are not needed inside the collar 30, which leave the internal dimension clean of excess cement after closure.
The internal sleeve 40 is opened and closed by engaging the collet-shifting tool 54 made up on the workstring 52. The tool 54 is usually placed between opposed cups (not shown) on a service tool 50.
In FIG. 4B, the shifting tool 50 is manipulated uphole by the workstring 52 to open the collar's sleeve 40 relative to the port 36. When the shifting tool 50 is moved and the collets engage the sleeve's profile 48b, the sleeve 40 can shift to the open position. When the sleeve 40 is open, a primary cement job can be performed by pumping down the workstring 52, out the service tool 54, through the open port collar 30, and into the annulus around the casing or liner.
Finally, as shown in FIG. 4C, the shifting tool 50 manipulated downhole by the workstring 52 can shift the port collar's sleeve 40 closed, which may be subsequently locked in place. On completion of the cement job, for example, axial movement of the tool 50 closes the sleeve 40 and seals the port collar 30 closed. The service tool 50 is then retrieved from the well, leaving the internal dimension of the port collar 30 full-bore to the casing or liner and free from of cement and other debris.
In deviated holes, the workstring 52 and shifting tool 50 may not actually manipulate the sleeve 40 open or closed inside the mechanical port collar 30. In fact, to function properly, the mechanical port collar 30 can require the workstring 52 to locate the shifting tool 50 at a certain point in the collar 30. Typically, operators determine proper location of the shifting tool 50 on the rig floor using force indications on a weight indicator. This may not always be effective. Therefore, being able to open and close a mechanical port collar without needing to particularly locate a workstring and shifting tool would be of great value to cement operations.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.